A prominent feature of modern typewriters is an error correction feature in which tapes or ribbons are struck with the erroneous letter or letters, and the errors are either covered up or are lifted from the paper. The correction ribbons are "one-time" products, good for one erasure per character space, and fresh ribbon must be supplied as needed for erasing operation. Accordingly, cassette arrangements are provided for such correction ribbons and require ribbon tensioning mechanisms for maintaining a substantially constant tension of the ribbon to prevent the ribbon from drooping and interfering with the printing mechanism and/or printing ribbon of the typewriter.
The prior art is replete with ribbon tensioning mechanisms, such as, for example, U.S. Pat. Nos. 2,202,958; 4,273,454 and 4,605,327. However, the known mechanisms require a multiplicity of parts, or are delicate, or require adjustments or are difficult to assemble.